In a LTE evolution system (LTE-A), A primary technology, to support a higher cell average throughput and a higher cell border throughput, is coordinated multiple point transmission (CoMP). According to the present discussion, there are two types of CoMP technologies including coordinated multiple point scheduling (CoMP CS) and coordinated multiple point joint processing (CoMP JP). To CoMP CS, the data of user equipment (UE) is from a sending node, i.e. serving cell while signals sent by other sending nodes are equivalent to interference. So that, it is necessary to perform a coordinated scheduling between multiple sending nodes to control the interference level; to CoMP JP, multiple sending nodes send data to a UE at the same time-frequency resource location, so that it is possible to improve the signal-to-noise ratio of UE signal and reduce the interference.
In a mobile communication system, a set of cells measured by a UE, i.e. measuring group is configured in the network to support operations such as radio resource management. At the same time, to CoMP, it is necessary for the network to determine which sending nodes sending signals to a UE. In the current standards, two cell group concepts, associated with CoMP, are defined. To a UE working in the mode of CoMP (referred to as CoMP UE in general), a set of cells, to be measured and of which the channel information should be reported, are configured in the network. The set of cells are referred to as report set. At the same time, report sets corresponding to the different UEs include the different cells. The number of cells included in a reporting set determines the overhead of a UE sending an uplink signaling of channel feedback information. Since the number of cells included in the reporting set may be large, a CoMP UE may also select to only report the channel information of a part of cells in a reporting set. The part of cells is regarded by the network as a set of cells for practically sending signals to a UE, which is referred to as cooperating set. It is easily understood that, to the same UE, its cooperating set may be the same as its reporting set, or a subset of its reporting set.
In a LTE-A system, there are two types of common reference signals, one is a CRS for use in channel estimation, the type of signal follows the structure defined in the LTE system; the other one is a reference signal (CSI-RS) for use in channel measurement, the type of signal is a new signal type defined in the LTE-A system. A design principle for CRS and CSI-RS requires the adjacent cells sending the CRS and CSI-RS at the different time-frequency resource, so that there is no interference among the CRS and CSI-RS sent by the adjacent cells. The advantage brought by this design principle is that, the adjacent cells may respectively improve the transmit powers of their CRS and CSI-RS, so as to improve the precision of channel estimation and channel measurement.